I'll give the city credit for trying to make this work. Although you can just rent it to your friend on a long term tenancy agreement and then have them rent it out on Airbnb...

There are restrictions on AirBnB itself. The authorities could also review the status of the apartment if there are AirBnB violations. I certainly hope that the city goes 101% on enforcement.

Airbnb and empty homes tax are two different things. If I rent my condo to someone else, who in turn rents on Airbnb while they travel or whatever...not much the city can do, except hunt down those listings and go after them for Airbnb violations, which would be a lot of work for little return. Also some Airbnb owners may elect to pay empty homes tax and continue renting the unit out if it nets enough income.